On Sat, Sep 30, 2023 at 12:39:43AM +0200, Laurenz Albe wrote:
> On Fri, 2023-09-29 at 18:08 -0400, Bruce Momjian wrote:
> > On Wed, Sep 6, 2023 at 05:53:56AM +0200, Laurenz Albe wrote:
> > > > We may have different mental models here. This relates to the part
> > > > that I wasn't keen on in your patch, i.e:
> > > >
> > > > + The partitions of a partitioned table are normal tables and get
> > > > processed
> > > > + by autovacuum
> > > >
> > > > While I agree that the majority of partitions are likely to be
> > > > relkind='r', which you might ordinarily consider a "normal table", you
> > > > just might change your mind when you try to INSERT or UPDATE records
> > > > that would violate the partition constraint. Some partitions might
> > > > also be themselves partitioned tables and others might be foreign
> > > > tables. That does not really matter much when it comes to what
> > > > autovacuum does or does not do, but I'm not really keen to imply in
> > > > our documents that partitions are "normal tables".
> > >
> > > Agreed, there are differences between partitions and normal tables.
> > > And this is not the place in the documentation where we would like to
> > > get into detail about the differences.
> > >
> > > Attached is the next version of my patch.
> >
> > I adjusted your patch to be shorter and clearer, patch attached. I am
> > planning to apply this back to PG 11.
>
> Thanks for looking at this.
>
> I am mostly fine with your version, but it does not directly state that
> autovacuum does not process partitioned tables. I think this should be
> clarified in the beginning.
Very good point! Updated patch attached.
--
Bruce Momjian <br...@momjian.us> https://momjian.us
EDB https://enterprisedb.com
Only you can decide what is important to you.
diff --git a/doc/src/sgml/maintenance.sgml b/doc/src/sgml/maintenance.sgml
index 9cf9d030a8..be1c522575 100644
--- a/doc/src/sgml/maintenance.sgml
+++ b/doc/src/sgml/maintenance.sgml
@@ -861,10 +861,16 @@ analyze threshold = analyze base threshold + analyze scale factor * number of tu
</para>
<para>
- Partitioned tables are not processed by autovacuum. Statistics
- should be collected by running a manual <command>ANALYZE</command> when it is
- first populated, and again whenever the distribution of data in its
- partitions changes significantly.
+ Partitioned tables do not directly store tuples and consequently
+ autovacuum does not <command>VACUUM</command> them. (Autovacuum does
+ perform <command>VACUUM</command> on table partitions just like other
+ tables.) Unfortunately, this also means that autovacuum doesn't
+ run <command>ANALYZE</command> on partitioned tables, and this
+ can cause suboptimal plans for queries that reference partitioned
+ table statistics. You can work around this problem by manually
+ running <command>ANALYZE</command> on partitioned tables when they
+ are first populated, and again whenever the distribution of data in
+ their partitions changes significantly.
</para>
<para>
